This is "Breathe" by Marie Barnett and as performed by Michael W. Smith.  This arrangement is very similar to the original recording though there are a few minor differences.  This includes a piano/synth part, 3 part vocal and a Violin Obligato or descant part as played on the recording. 

YOU NOW Get FOUR Keys  Bb/C, C/D, F/G and A/B.  Note that the Bb/C version comes also with a full score but the C/D, F/G and A/B only have the parts.

Be sure to download a score sample and audio sample of the original recording.